The objective of the research proposed herein is to fractionate the cellular basis for this immune response to tumor grafts into 2 components; helper (tumor suppressive) and harmer (immuno-suppressive); to further fractionate these components into T and B cell function. In addition, we plan to determine the mechanism by which a number of factors affect the balance of these two antagonistic effects, both by host and tumor modification. The principal tumor modifications will be chemical modifications of the tumor membrane with specific glycosidases, haptens, fixatives and drugs. Host modifications will consist of deprivation of various cellular elements, which participate in the immune response (T cells, including T1 and T2, B cells and macrophages). We will also make a careful study of how surgical removal of tumors may affect the subsequent immunity. We also plan to specifically investigate how tumor cells, complexed with enhancing antibody, might affect the development of suppressor T cells. Techniques to be used include density gradient separations, adoptive transfers of immunocompetent cells, thymectomies, splenectomies, irradiation, and in vitro assays of immunity. BIBLIOGRAPHIC REFERENCES: Gershon, R. K. The role of suppression in immmunoregulation. In: Immune Reactivity of Lymphocytes: Development, Expression and Control (M. Feldman and A. Globerson eds.) Plenum Press, N.Y. 1976 pp 557-563. Gershon, R. K. Suppressive interactions between different MLR loci. In: The Role of Products of the Histocompatibility Gene Complex in Immune Responses. (D. H. Katz and B. Benacerraf, eds.) Academic Press, N.Y. 1976. pp. 193-202.